Japanese Patent Application Laid-Open (JP-A) No. H08-323843 describes a parison molding apparatus in which molten resin is passed through a resin flow path formed by a core and a die, and the size of a flow-regulating portion of the resin flow path is changed and the thickness of a parison is adjusted by causing plural divided ring portions provided in a ring-shaped groove of the die to slide.
In the parison molding apparatus, the divided ring portions are each caused to slide by a cylinder through a link portion. The divided ring portions are each lowered when a rod of the cylinder advances forward.